I'm pretty sure I can solve your problem. You see, WordPress sends several Set-Cookie headers when you try to log in. HttpWebRequest only handles one instance of this header, so some cookies are lost. It's true that usPlus

It is possible to login to wordpress with the HttpWebRequest object and I can show you how. I am not pretty sure, I am sure. ZakTheFallen is incorrect because if you handle the cookies yourself with the CookieContainerPlus